package com.test.gateway.config;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;

import com.netflix.hystrix.HystrixThreadPoolKey;
import com.netflix.hystrix.HystrixThreadPoolProperties;
import com.netflix.hystrix.strategy.HystrixPlugins;
import com.netflix.hystrix.strategy.concurrency.HystrixConcurrencyStrategy;
import com.netflix.hystrix.strategy.concurrency.HystrixRequestVariable;
import com.netflix.hystrix.strategy.concurrency.HystrixRequestVariableLifecycle;
import com.netflix.hystrix.strategy.eventnotifier.HystrixEventNotifier;
import com.netflix.hystrix.strategy.executionhook.HystrixCommandExecutionHook;
import com.netflix.hystrix.strategy.metrics.HystrixMetricsPublisher;
import com.netflix.hystrix.strategy.properties.HystrixPropertiesStrategy;
import com.netflix.hystrix.strategy.properties.HystrixProperty;


public class FeignHystrixConcurrencyStrategy extends HystrixConcurrencyStrategy {  

	private static final Logger log = LoggerFactory.getLogger(FeignHystrixConcurrencyStrategy.class);  
	private HystrixConcurrencyStrategy delegate; 
	
	public FeignHystrixConcurrencyStrategy() {  
		try {  
			this.delegate = HystrixPlugins.getInstance().getConcurrencyStrategy();  
			if (this.delegate instanceof FeignHystrixConcurrencyStrategy) {  
				// Welcome to singleton hell...  
				return;  
			}  
			HystrixCommandExecutionHook commandExecutionHook =  
					HystrixPlugins.getInstance().getCommandExecutionHook();  
			HystrixEventNotifier eventNotifier = HystrixPlugins.getInstance().getEventNotifier();  
			HystrixMetricsPublisher metricsPublisher = HystrixPlugins.getInstance().getMetricsPublisher();  
			HystrixPropertiesStrategy propertiesStrategy =  
					HystrixPlugins.getInstance().getPropertiesStrategy();  
			this.logCurrentStateOfHystrixPlugins(eventNotifier, metricsPublisher, propertiesStrategy);  
			HystrixPlugins.reset();  
			HystrixPlugins.getInstance().registerConcurrencyStrategy(this);  
			HystrixPlugins.getInstance().registerCommandExecutionHook(commandExecutionHook);  
			HystrixPlugins.getInstance().registerEventNotifier(eventNotifier);  
			HystrixPlugins.getInstance().registerMetricsPublisher(metricsPublisher);  
			HystrixPlugins.getInstance().registerPropertiesStrategy(propertiesStrategy);  
		} catch (Exception e) {  
			log.error("Failed to register Sleuth Hystrix Concurrency Strategy", e);  
		}  
	}  

	private void logCurrentStateOfHystrixPlugins(HystrixEventNotifier eventNotifier,  
			HystrixMetricsPublisher metricsPublisher, HystrixPropertiesStrategy propertiesStrategy) {  
		if (log.isDebugEnabled()) {  
			log.debug("Current Hystrix plugins configuration is [" + "concurrencyStrategy ["  
					+ this.delegate + "]," + "eventNotifier [" + eventNotifier + "]," + "metricPublisher ["  
					+ metricsPublisher + "]," + "propertiesStrategy [" + propertiesStrategy + "]," + "]");  
			log.debug("Registering Sleuth Hystrix Concurrency Strategy.");  
		}  
	}  

	@Override  
	public <T> Callable<T> wrapCallable(Callable<T> callable) {  
		RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();  
		return new WrappedCallable<>(callable, requestAttributes);  
	}  

	@Override  
	public ThreadPoolExecutor getThreadPool(HystrixThreadPoolKey threadPoolKey,  
			HystrixProperty<Integer> corePoolSize, HystrixProperty<Integer> maximumPoolSize,  
			HystrixProperty<Integer> keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {  
		return this.delegate.getThreadPool(threadPoolKey, corePoolSize, maximumPoolSize, keepAliveTime,  
				unit, workQueue);  
	}  

	@Override  
	public ThreadPoolExecutor getThreadPool(HystrixThreadPoolKey threadPoolKey,  
			HystrixThreadPoolProperties threadPoolProperties) {  
		return this.delegate.getThreadPool(threadPoolKey, threadPoolProperties);  
	}  

	@Override  
	public BlockingQueue<Runnable> getBlockingQueue(int maxQueueSize) {  
		return this.delegate.getBlockingQueue(maxQueueSize);  
	}  

	@Override  
	public <T> HystrixRequestVariable<T> getRequestVariable(HystrixRequestVariableLifecycle<T> rv) {  
		return this.delegate.getRequestVariable(rv);  
	}  

	static class WrappedCallable<T> implements Callable<T> {  
		private final Callable<T> target;  
		private final RequestAttributes requestAttributes;  

		public WrappedCallable(Callable<T> target, RequestAttributes requestAttributes) {  
			this.target = target;  
			this.requestAttributes = requestAttributes;  
		}  

		@Override  
		public T call() throws Exception {  
			try {  
				RequestContextHolder.setRequestAttributes(requestAttributes);  
				return target.call();  
			} finally {  
				RequestContextHolder.resetRequestAttributes();  
			}  
		}  
	}  
}  